1. Field of the Invention
This invention relates to latching devices and, in particular, to flush-mounted latching devices for use in interior doors of aircraft and similar applications where size, weight, durability, and ease of operation are of particular concern.
2. Description of the Related Art
Various latching devices are known for opening and closing doors. The most commonly known latching device is the conventional doorknob. By this familiar device a door may be opened or closed by turning or twisting a knob or handle on either side of a door to retract a wedge-shaped bolt which secures the door to the door frame. When the bolt is extended, it engages a corresponding strike mounted in the door frame to prevent the door from opening. When the bolt is retracted, the door may be swung open by application of a pulling or pushing force.
In aircraft or similar applications where space is limited (e.g., buses, motor-homes, automobiles, boats, etc.), it is desirable to provide a latching device that can be mounted flush with the door surface. Flush mounting eliminates the need to provide additional space to accommodate handles or knobs used to operate conventional door latching devices. Flush mounting is also desirable from a safety standpoint since it prevents injury to passengers from protruding knobs or handles during turbulent periods of flight in an aircraft or other injuries incident to cramped conditions within a moving vessel.
One type of flush-mounted latch known in the aircraft and automotive industry is based upon a retractable handle design. Most commonly, a hinged actuator handle or lever is pivotably mounted within a recessed cavity in the door. In its retracted position the actuator lies more-or-less flush with the door surface. In operation the handle is swung outward from the door surface to release the latch mechanism, allowing the door to be pushed or pulled to its open position. See, for instance, U.S. Pat. No. 4,025,096, assigned to Adams Rite Products, Inc., which discloses a latching device for cabinet doors having a swingably retractable handle. Other latch designs require the handle to be swung outward from the door surface and then either turned or rotated to release the latch mechanism.
A problem with retractable-handle type latching devices is that the exposed operating provisions tend to be subjected to a variety of abuse loads by operators. This results in frequent failures of the handles and latch mechanisms making them undesirable for commercial aircraft and similar uses. Moreover, the inherent nature of these types of devices is such that a certain degree of strength and dexterity is required to operate them. This may present a substantial obstacle for elderly or physically disabled persons, for example.
A second type of flush-mounted latch, having no exposed operating provisions, is known in the stereo cabinet industry. Typically, the latching of a glass cabinet door is accomplished by pushing the door against a spring-loaded latch which retains a magnet at its tip. The door is equipped with a corresponding ferromagnetic plate that is drawn to the magnet to retain the door when it is in its closed position. When the door is pushed in and then released, the latch springs outward accelerating the door away from the cabinet. When the latch reaches its end-of-travel, an inertial force is created in the door sufficient to break the magnetic force retaining the door, allowing it to swing free.
One drawback of magnetic latches is that they do not provide a positive lock. In other words, a closed door may be forced open without first releasing the latch. This characteristic is highly undesirable in aircraft and similar applications, since a door opening during flight could cause injury to passengers or allow luggage or other objects to fall free from their containers. Moreover, the vibrational and shock forces generated in an aircraft would easily exceed the retaining forces present in most magnetic latches. Another drawback of magnetic latches is that they typically are only designed to be actuated from the exterior side of a door and so are not suitable for use in applications requiring two-sided operation of a door.
Accordingly, there is a need for a positive-locking latch that can be mounted flush with a door surface, can be operated from both sides of the door, is easily used by elderly or physically disabled persons, and is not easily damaged. In particular, there is a need for a flush-mounted latch that can be operated within the five pound maximum load requirement prescribed by the ADA guidelines, 35658 Federal Register, Section 4.27.4, of Volume 56, No. 144.